Telephone-receiver.



Patented Aug. l9,' I902.

-' .L. MELLETT.

TELEPHONE RECEIVER.

(Application filed. July 6, 1901.1

No Model.)

my; Noam: versus cu mom-mine wmmuron. bic.

' IJNTTED STATES PATENT OFFICE.

LEMUEL MELLETT, OF SOMERVILLE, MASSACHUSETTS, ASSIGNOR TO THE AMERICAN OTOPHONE COMPANY, OF BOSTON, MASSACHUSETTS, A COR- PORATION OF MAINE.

TELEPHONE-RECEIVER.

SPECIFICATION forming part of Letters Patent No. 707,441, dated August 19, 1902.

Application filed July 5, 1901. Serial No. 671080. (No model.)

To (6Z5 whom it may concern:

Be it known that I, LEMUEL MELLETT, of Somerville, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements in Telephone-Receivers, of which the following is a specification.

This invention relates to telephone-receivers; and its object is to increase the power 10 or sound-giving property and also the sensitiveness of such instruments.

Of the accompanying drawings, forming a part of this specification, Figure 1 represents a front elevation of a telephone-receiver constructed in accordance with my invention with its cover and diaphragm removed to expose the interior. Fig. 2 represents a section on line 2 2 of Fig. l.

The same reference characters indicate the same parts in both figures.

My invention is designed to improve both the acoustic and electromagnetic properties of a receiver.

1 is a cup-shaped steel casing, in the conter of which is fixed a steel magnet-core 2, surrounded by a wire bobbin or winding 3, having electrodes 4 at united in a cord 5, which passes outside of the casing through a hole in the latter. The casing 1, core 2, and

winding 3 constitute a polarized electromag net having one pole at the free extremity of the core 2 and the other pole at the free annular edge of the casing 1.

6 represents a soft-iron diaphragm having its edges in contact with the rim of the easing 1 and its center close to but out of contact with the end of the core 2.

7 is a vulcanite cover screwing on the easing 1 and having a central hole 8 to expose the diaphragm. It will be noted that the edges of the cover 7 do not screw down tight against the edges of the diaphragm 6, so as to clamp said diaphragm, but are removed a distance therefrom, so as. to leave the diaphragm loose. I

Making the receiver-magnet with an annular pole-piece in the manner described efitects several objects. First, it provides for a deeper air-column and one of greater volume behind the diaphragm than is ordinarily obtained,

and thus increases resonance; second, since there is but one pole-piece back of the center of the diaphragm the flux of magnetic lines of force is more concentrated upon the diaphragm than with two pole-pieces of the requisite size located behind the diaphragm center, and a better vibratory effect is thereby obtained; third, no loss in magnetic eiiect is observed, but a gain, since the wide removal of the poles from each other compels practi- 6o cally all of the lines of force to pass through the diaphragm 6 and since also there is but a single air-gap in the magnetic circuit namely, that between the diaphragm 6 and the end. of the core 2. By leaving the edges of the diaphragm free a greater area of said diaphragm is utilized than where said edge is more or less rigidly clamped. My construction does away with the necessity or desirability of suspending the edges of the diaphragm between felt or other yielding washers, since the attraction of the annular polepiece underneath said edge aitords a sufiicient anchorage for the edge of the diaphragm without adding appreciably to the rigidity of the central portions away from said edge.

The center of the diaphragm 6 is shown as supported between two conical coiled springs 9 10, whose adjacent ends abut opposite sides of the diaphragm, while their remote ends are confined, respectively, by the cover 7 and the top of the bobbin 3. The outer spring 9 counteracts the outward pressure of the inner spring 10; but the inner spring opposes the attractive force of the magnet-core 2 and keeps 8 5 the diaphragm from being drawn against said core. The diaphragm is thus in a measure suspended in space by the springs 9 10, and I am enabled to use a thinner diaphragm and bring it closer to the magnet-pole than is the case where the rigidity of the diaphragm is relied on to hold it away from the magnetpole. A thinner diaphragm will vibrate more freely in all portions, and thus give better acoustic effects.

In the space behind the diaphragm 6 I 10- cate a series of harmonic vibrators 11 12, having their outer ends secured to the side Wall of the casing 1 and their inner ends left free to vibrate and directed radially inward to- I00 ward the center of the casing. These vibrators, which are shown both in the form of reeds and of small helical springs, are of different lengths, so as to emit diiferent fundamental tones when vibrated, and are shown as sixteen in number, corresponding to two octaves. A greater or less number of vibrators may be provided or vibrators of a different character. When the diaphragm 6 is set in vibration by a magnetic impulse received in the electromagnet, emitting a given tone or tones, one or more of the vibrators 11 12 will be sympathetically or consonantly vibrated and will have the effect of reinforcing and perpetuating the vibration of the diaphragm, and thus increasing the loudness of the tone emitted thereby. In connection with a receiver of this character the best results are obtained by employing a transmitter constructed as described in a patent, No. 667 ,546, granted to me February 5, 1901, and tuning the vibrators in each instrument alike.

I claim 1. In a telephone hearing-receiver, a magnetic diaphragm, electromagnetic means exerting attraction on said diaphragm, the receiver being provided with such means on one side only of the diaphragm, spring means ex erting an outward pressure on the diaphragm in opposition to the magnetic attraction, and

spring means exerting inward pressure on the diaphragm in opposition to the pressure of the first said spring means, substantially as and for the purpose described.

2. In a telephone hearing-receiver, a magnetic diaphragm free at its edges, a magnet cooperating with the diaphragm on one side thereof and springs acting in opposition to each other on the diaphragm.

3. In a telephone hearing-receiver, a magnetic diaphragm, a magnet cooperating with said diaphragm on one side thereof, aspring on the inner side of the diaphragm acting in opposition to the attraction of the magnet, a spring on the outer side of the diaphragm acting in opposition to the first said spring, and an apertured cover for the outer side of the diaphragm forming an outer support for the last said spring.

4. In a telephone-receiver, a diaphragm, a magnet operating behind the diaphragm to directly vibrate the same, and a series of differently-tuned harmonic vibrators located behind the diaphragm.

In testimony whereof I have affixed my signature in presence of two witnesses.

LEMUEL MELLETT.

WVitnesses:

R. M. PIERSON, M. 13. MAY. 

